Tertiary Structures

1
Tertiary Structures

• Cf myoglobin, RNAse, cytochrome C, and lysozyme
• Mb high age of ?-helix
• Cytochrome C less ?-helix, some ?-sheet.
• RNAse more ?-sheet
• Lysozyme both in good measure

2
Figure 6-18
3
6-18 b
4
6-18c
5
Interior of protein

• Interior contains mostly hydrophobic residues
  which stabilize structure,
• But small proteins need more bonds
• Disulfide
• Other prosthetic groups (heme, e.g.) covalently
  attached

6
Table 6-2
7
Supersecondary structures (motifs or folds)

• Combinations which recur
• Organization of structures (SCOP)

8
Folding regularities (not exhaustive)

• ?-?-? loop
• ?-? corner

9
6-20a
10
6-20a (right)
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Folding regularities (cont)

• ?-helices and ?-sheets usually are found in
  different layers (they dont readily H-bond to
  each other)

12
Folding regularities (cont)

• Polypeptide chains adjacent in primary structure
  usually adjacent in tertiary structure

13
Folding regularities (cont)

• No crosses or knots

14
6-20b (left)
15
6-20b (right)
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Folding regularities (cont)

• The ? conformation most stable with a right hand
  twist
• ? sheets have a crossover strand, which usually
  is a right handed connection
• Twisting larger scale structures result

17
6-20d
18
6-21a
19
6-22
20
6-22
21
6-22
22
6-22
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SCOP

• Class
• Fold
• Family- significant primary sequence similarity
  and/or similar structure and function (globins,
  e.g.)
• Superfamily significant structural and
  funcional similarity (little primary structure
  similarity)

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Quaternary Structure

• Multimers
• Dimers
• Oligomers
• Protomers